Modern internal combustion engines, equipped with carburetors, rely for the supply of fuel to the cylinders upon vacuum and air flow past a series of jets from which fuel is drawn in droplets, mixed with the incoming air and drawn into the individual cylinders. The overall air/fuel ratio is set to provide the cylinder with the leanest mixture a sufficient air/fuel ratio to secure ignition. This requirement forces some of the cylinders to operate on much richer mixtures, which results in poor combustion efficiencies in these fuel rich cylinders. In addition, manifold vacuum, which to a major extent governs the amount of fuel drawn into the engine, behaves in a manner opposed to the fuel requirements of the engine. During acceleration, manifold vacuum decreases causing less fuel to be drawn into the engine, while at the same time lowering the dew point of the air/fuel mixture in the manifold and causing the precipitatiin of some of the fuel droplets from the mixture, the amount of droplets leaving the mixture being somewhat dependent upon the distance from the venturi section of the carburetor to the cylinders. This phenomenon requires the presence of an accelerating pump to supply fuel to the engine in order to overcome the defficiency of the supply of fuel. Upon deceleration, the manifold vacuum rapidly increases, drawing an excess of fuel into the intake manifold and causing an extra-rich mixture. Even at steady state engine speed operation, mixture ratios vary, especially with engine load changes, and non-uniform mixtures from cylinder to cylinder exist due to the behavior of gas and liquid mixtures and the impossibility of uniformly maintaining them during the transport from one end of the intake manifold to the other.
The teachings of our invention provide means for correcting all of these conditions which cause excessive fuel consumption and the discharge of exhaust pollutants to the atmosphere. In this electronic controlled manifold injection system, the amount of fuel delivered to the engine under all under all operating conditions is determined by the speed and delivery of the positive displacement fuel pump. The speed of this pump is controlled at all operating conditions of the engine by sensing the weight of the air being drawn into the engine and the weight of the fuel being delivered by the fuel pump, and by varying the speed and hence the fuel delivery from the pump until the weight of the delivered fuel is at the pre-determined ratio to the weight of the air. The only fuel to enter the engine is that forced into it by this injection pump. Therefore, variations in manifold vacuum, engine speed and other variables such as temperature, humidity and atmospheric pressure are all compensated for by making the supply of fuel controlled by the weight of air entering the engine.
The art of raising liquid fuel to a temperature level, thereby causing it to substantially reach its distillation point, or vaporize, when it is introduced to a partial vacuum, is well known. Several patents involving this principle have been granted in the past, and the principle is now a part of public domain. It is also a well known fact that a gas and gas mixture has a chance of being a better, more stable mixture than that of a liquid and a gas. Some of the past carburetor designs have attempted to take advantage of air and vaporized fuel mixtures in internal combustion engines in which the air and the fuel are mixed just prior to their entrance to the intake manifold and transported as a mixture to the cylinders. These devices were conceived to deliver superior mixture of the air and fuel, and thereby provide enhanced distribution characteristics of the mixture to all of the cylinders of the engine, but they lacked a means for accurately controlling temperatures of the liquid or gaseous fuel and for accurately controlling the ratio of air to fuel. A few patents disclosed the use of exhaust gases for heating the fuel, and others utilized hot water from the cooling system or battery power from the electrical system to heat the fuel electrically. Each of these systems suffered from various disadvantages such as the time required to raise the fuel to its required temperature, a difficulty of controlling the necessary range of temperature of the fuel and, in the case of the electric heater, a problem of consuming large wattages, placing hardships on components of the electrical system. The subject invention utilizes either of two methods provided to heat the fuel. These methods are, (1) exhaust gases and electrical power through a heat exchanger or (2) hot water from the cooling system and electrical power through a heat exchanger; with either the hot exhaust gas or hot water being used to raise substantially the temperature of the fuel and the electrical heater being used incrementally to add temperature in smaller quantity but sufficiently to control the required temperature of the hot, liquid fuel. The ultimate temperature of the fuel is controlled by a solid state proportional electronic circuit, which is hooked up to the heating element of the electric heater.
The concept of using electronics to control temperature and, especially, air/fuel ratio in the subject invention was selected because of the inherent accuracies obtainable by using this method of control. In addition, an important feature of symmetrical conditions of air and fuel flow from the centrally located manifold injector is obtained by providing two counter-rotating intake air throttles with the fuel injection tube located below the twin throttles.